relativity wins
Hi upsangel,
"The system includes:
A single channel TCAS computer
Two TCAS antennas
Two mode S ATC transponders, one active the other in standby.
These transponders allow:
o
Interface between the ATC/TCAS control panel and the TCAS computer
o
Communication between the aircraft and intruders equipped with a TCAS system.
The TCAS interrogates transponder of intruders. From the transponder replies, the TCAS determines for each intruder:
Its relative bearing
Its range and closure rate
Its relative altitude if available (ATC mode C or S)
Then the TCAS computes the intruder trajectory, the Closest Point of Approach (CPA) and the estimated time (TAU) before reaching the CPA.
Each time the relative position of the intruder presents a collision threat, aural and visual advisories are triggered.
TCAS optimizes vertical orders to ensure a sufficient trajectory separation and a minimal vertical speed variation considering all intruders."
Logic 2 is correct.